Changes in stature and spine kinematics during a loaded walking task

Area of Science:

• Biomechanics
• Occupational Health
• Spinal Kinematics

Background:

• Asymmetric load carriage is common in occupations such as mail delivery.
• The biomechanical effects of carrying such loads on spinal kinematics and stature are not fully quantified.

Purpose of the Study:

• To quantify spinal kinematics and stature loss during asymmetric load carriage.
• To evaluate the impact of a standard Royal Mail bag on spinal posture and height.

Main Methods:

• Six healthy males walked 8,500m with and without a 17.5% body mass mailbag.
• Spinal kinematics (forward leaning, lateral bending) and stature loss were measured.
• Load was gradually reduced during the task.

Main Results:

• Loaded conditions resulted in double the stature loss compared to unloaded conditions.
• Significant forward leaning (up to 6°) and lateral spinal bending (up to 12°) were observed with the load.
• Thoracic spine adjusted in the sagittal plane; lumbar spine adjusted in the frontal plane.

Conclusions:

• Asymmetric mailbag use induces substantial spinal deformation and height reduction.
• Current mailbag designs that prevent alternating sides are detrimental.
• Recommendations for improved mailbag design to promote load alternation are suggested.